Conventionally, an electrical resistance-type PM sensor that detects PM in an exhaust gas discharged from an internal combustion engine has been known. In general, the electrical resistance-type PM sensor has a pair of conductive electrodes arranged to face each other on a surface of an insulation substrate and estimates a PM amount by using a change in an electrical resistance value caused due to conductive PM (mainly, soot component) attached to the electrodes (for example, refer to Patent Document 1).